This invention relates to an apparatus and method for alleviating or preventing excessive pressure, and therefore pressure sores, from developing on a contacted area of a person's body. More particularly, the invention relates to a seat cushion for a personal mobility vehicle, wherein the cushion has a pressure-distributing medium for alleviating or preventing excessive pressure from developing on a contacted area of the user's body.
A pressure sore is any lesion caused by excessive, unrelieved pressure on an area of a person's body. When pressures above normal homeostatic pressure are applied to a region of the person's body and its associated blood vessels, the blood vessels can partially or fully collapse, thereby disrupting normal circulation. As a result, the affected area becomes devoid of blood supply, which prohibits oxygen and nutrients from being delivered to the surrounding tissue. Pressure sores often occur over bony prominences of the person and can range in severity from partial thickness skin loss to full thickness skin loss with tissue necrosis and damage to underlying muscle and bone.
Pressure sores are a common and costly problem in wheelchair occupants. Various areas of the occupant's body may be permanently or almost permanently in contact with the support surface of the wheelchair, resulting in excessive pressure, lack of air circulation, and often increased shear between the contacted area of the occupant's body and the support surface.
Various systems have been proposed to reduce or prevent pressure sores. Among the most common prevention systems are cushions or pads that include some type of raised surface that is designed to lower the pressure between the bony prominences and the support surface and equalize the pressure over the entire surface in contact with the occupant's body. In order to be effective in this capacity, the raised surface is designed to keep the bony prominences away from the support surface. However, upon the application of pressure by contact with the occupant's body, the raised surface tends to compress so that the bony prominences rest against the support surface anyway. This action negates any lowering of pressure of the affected area, while also decreasing aeration and increasing the potential for shear between the occupant's body and the cushion.
More sophisticated support surfaces employ a pressure-distributing medium in combination with a cushion base. The most common medium is a fluid pad that is positioned on top of the base. The fluid pad moves with the occupant's body to continually maintain an even distribution of the occupant's weight across the surface of the cushion base.
Conventional fluid pads are held in a fixed relation to the cushion base by enclosing the pad in an envelope and attaching the envelope to the base with hook-and-loop fasteners or by providing an inner cover for covering the base and attaching the pad to the cover with hook-and-loop fasteners.
What is needed is a support surface that eliminates the need for an envelope or an inner cover and thus requires fewer production materials and reduces production costs.